The present invention relates to transformer devices comprising a saturable core having control and controlled windings, the saturable core being controlled in a feedback mode by switch means.
Means for detecting dc current have been known in which a resistance element is inserted in the path of the current to be detected and a voltage drop across the resistance element is measured in place of current, A dc transformer is commonly used when the current is desired to be detected indirectly from the circuit carrying the current.
The prior art transformer device is unable to identify the polarity of the current or voltage detected unless by providing the saturable cores with a third winding through which the voltage phase is detected. Another prior art approach has been to use a Hall element. In practice, however, the Hall output accompanies a considerable ripple each time one of the two saturable cores is saturated. Another known approach has depended upon the use of a magnetic responsive element which, however, is not stable enough against variations in ambient temperature.